Taco Cowboy writes: When most ocean waves collide, the "interaction height" is usually the sum of the incoming wave heights. But in the case of interaction between X- and Y-shaped ocean waves, the wave heights that result from such interactions turn out to be much taller, indicating that they may in the nonlinear category.

Satellite observations of the 2011 tsunami generated by the devastating earthquake that struck Japan indicate there was an X-shaped wave created by the merger of two large waves. If the interaction had happened at a much greater distance from shore, the devastation could have been even worse as the amplitude could have been even larger. Not every tsunami is strengthened by interacting waves, but when they do intersect there can be a powerful multiplier because of the nonlinearity.

Two mathematicians from the University of Colorado at Boulder, professor Mark Ablowitz and doctoral student Douglas Baldwin decided to investigate why some tsunamis are able to wreak so much havoc.

A paper on the subject by Ablowitz and Baldwin was published this month in the journal Physical Review E.

Ablowitz first observed the nonlinear wave action in 2009 while visiting Nuevo Vallarta just north of Puerto Vallarta with his family. He took hundreds of photographs and videos of the peculiar waves over the next several years.

"Unlike most new physics, you can see these interactions without expensive equipment or years of training," said Ablowitz. "A person just needs to go to a flat beach, preferably near a jetty, within a few hours of low tide and know what to look for."

Baldwin, who is studying under Ablowitz, wanted to verify that the wave interactions observed by his professor were not unique to one beach. He hit the jackpot at Venice Beach.

"I don't think there is anything more enjoyable in science than discovering something by chance, predicting something you haven't seen, and then actually seeing what you predicted," said Baldwin.